Automatically “Duck” Background Music Under Dialog in DaVinci Resolve

“Ducking” is the process of lowering the audio level of background music or background sounds during dialog. Resolve has a fascinating way to do this automatically – without keyframes. It’s called “sidechaining.”

NOTE: If you have a dialog clip with a lot of noise in it, ducking is not the right technique. To fix too much noise, you should use noise reduction, which Resolve also supports (Effects > Restoration > Fairlight FX > Noise Reduction).

To get started, here’s a sample edit, with three talking heads over a single music clip.

NOTE: This process would work with any number of music or sound effects clips. I’m just keeping it simple so you can see how this works.

This technique is called “sidechaining,” where the output of one audio track controls effects in a separate audio track. Not only is this blindingly fast to create, but it is highly flexible to configure for your project.

Here’s how.

THE PROCESS

Here’s what the mix looks like when you switch to the Fairlight page (shortcut: Shift + 7).

In the Mixer, double-click the Dynamics chart (red arrow) for the Music track; or whichever track holds clips whose level you want to drop when dialog occurs.

NOTE: To disable any dynamic effect, single-click the icon. A color icon means “enabled.” A gray icon means “disabled.” Single-click to toggle it on or off.

From the menu in the top left corner, select Music Pumper to create the initial configuration.

Here’s what the Dynamics window looks like so far.

Here’s the magic part. In the lower portion of the Compressor, where it says “Sidechain” click the Source menu and choose the track that contains dialog. (“Dialog” in my example.)

NOTE: If you have multiple tracks that contain dialog, combine them into a bus, then select that bus as the sidechain source.

When enabled, any dialog audio will trigger the compressor to lower the audio in the music track for as long as there is dialog audio.

For me, the default settings are too subtle. So, as you listen to the playback, lower the Threshold to decrease the audio levels of the music during dialog. (Remember, this uses negative numbers; larger numbers decrease audio levels more.) The amount will vary depending upon your specific clips. Also, tweak Ratio to determine the limit to the loudest passages of the music. Generally a setting between 3:1 and 5:1 will be sufficient.

Adjust these two settings until you get the results you want.

EXTRA FEATURES

If the audio level difference is too abrupt, boost the Knee to add more of a curve to the compression. It will be illustrated in the graph at the top of the Dynamics window.

To reset the Dynamics window, click this icon in the upper right corner.

To save your adjustments as a new setting, click the plus icon in the upper left corner.

When the On button is red, the sidechain is enabled. To disable side-chaining, click the On button to turn it gray. And, if you want to hear just the dialog that’s triggering the effect, for example to make sure you have connected the correct track, click the Listen button.

SUMMARY

And that’s it! Ducking will occur automatically whenever dialog occurs, without keyframes, without special metadata, even as you add, move, trim or delete clips. Very cool.

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